This invention relates to an X-ray tube for industrial use, more particularly to an X-ray tube used for the X-ray analysis and the applications thereof.
An X-ray tube for analytic use is constructed into a type of stationary anode wherein the anode including a target is hermetically secured to one end of an air-sealed envelope. The X-ray tube for analytic use is subject to long-hours continuous use when it is applied. Therefore, the target is heated upto high temperature and is subject to forced cooling with cooling medium such as water supplied to a cooler fitted to the anode.
A known X-ray tube for analytic use is shown in FIG. 1, in which X-ray tube 10 comprises an anode 16 hermetically secured to one end of an air-sealed envelope 14 and having a target 12 arranged integrally therewith, and a cooler 18 fitted on the outer surface of anode to cool the anode. The main body of the X-ray tube is constructed of the envelope 14, the anode 16 and a cathode. The electron-impact surface of anode target 12 is perpendicularly positioned with respect to the axis of X-ray tube, opposing the filament 20 of the cathode. The electrons emitted from the filament 20 impinge on an electron impact surface 12a, to form thereon a linear focus, for example, 1 mm in width and 10 mm in length. The X-rays generated on the focus are radiated in all directions in the surrounding space. For picking the radiated X-rays up, four windows 22 are disposed at the metal part of the envelope 14. As a result, from two windows positioned in the longitudinal direction of the above-mentioned linear focus, are radiated X-rays whose configuration at the focus is dotshaped, while from the other two windows positioned perpendicular to the longitudinal direction are radiated linear-shaped X-rays. These windows 22 are changeable-over according to the purpose of the use of X-ray tube.
The change-over of the windows is carried out by keeping the cooler 18 which concurrently serves as a fitting table in its stationary position and turning the main body of X-ray tube 10 through a degree of 90.degree..
The cooler 18 is made of a square plate, to whose central part is fixed an upright pipe 24 extended into the target 12. A flow passage 26 for supplying cooling medium to the upright pipe 24 is bored in the cooler 18. The cooling medium flows from an inflow passage 26a into the bottom part of pipe 24 and releases from the tip end of the pipe into the backside of the target corresponding to the electron-impact surface thereof, thereby cooling the target 12. The cooling medium after having absorbed the heat of the target 12 flows collectively into the outflow passage 26b to be discharged outside.
The upright pipe 24 is made of a cylindrical member having an inner diameter equal to or larger than the length of the focus in the longitudinal direction, so as to cool reliably the backside surface of target corresponding to the electron-impact surface of target, i.e., the focus, even when the main body of X-ray tube has been turned about the axis thereof. However, due to the large exit of cooling medium of pipe 24, a large quantity of cooling medium is necessary and the cooling efficiency is consequently low.
In order to raise the cooling efficiency to eliminate the above-mentioned disadvantages, as shown in FIG. 2 an X-ray tube 27 for analytic use is reported which comprises a bottomed cylindrical nozzle 30 provided at the bottom with a slit 28 having substantially the same shape and size as that of the focus and fitted over the upright pipe 24. The nozzle 30 is integrally provided with a plurality of, for example, four projection pieces 31 on the outer circumference of its bottom part so as to provide a cooling medium releasing space between the bottom of the nozzle and the target. Further, the nozzle 30 is integrally provided on its inner wall with a plurality of, for example, four axial pieces fitted into four axial grooves (not shown) formed in the outer periphery of the upright pipe 24 and spaced 90.degree. from each other in the circumferential direction of the nozzle so as to align the focus with the slit 28.
With this type of X-ray tube 25, the cooling medium is released through the slit which is brought into alignment with the focus and has substantially the same shape and size as that of the focus. Therefore, the released cooling medium collides with the whole backside surface of target corresponding to the focus thus making it possible to cool the target 12 effectively.
However, with the X-ray tube 25, when the main body thereof is set at a position turned 90.degree. with respect to its fitting table, i.e., the cooler 18, for picking a different focus shape of radiated X-rays up, the nozzle 30 has to be also turned simultaneously through a degree of 90.degree. so as to be fitted into the upright pipe 24.
If an operator should forget the corresponding turn of the nozzle 30, the released cooling medium will not strike against the whole corresponding backside surface of focus, resulting in the failure of sufficient cooling to cause the target 12 to be burned and damaged due to over-heating. Such danger is involved unavoidably in this type of X-ray tube 25.
It is therefore an object of this invention to provide an X-ray tube for analytic use capable of cooling the target effectively without causing damages to the same due to overheating. For achieving the aforesaid purpose, the X-ray tube for analytic use according to the present invention comprises a nozzle with slit, the nozzle detachably fitted to an anode so as to align the slit with the focus of electron impact surface of target. Since the nozzle is attached to the anode, when the main body of X-ray tube is turned, the nozzle is nescessarily integrally turned jointly with the anode as one part of the main body whereby the alignment of the slit and the focus always is necessarily kept thus to prevent the target from being damaged due to overheating.
Other objects, features and advantages of this invention will become apparent as the description thereof proceeds when considered in connection with the accompanying drawings..